Church, Alonzo (1903–95)

Alonzo Church was one of the twentieth century’s leading logicians. His work covers an extensive range of topics in logic and in other areas of mathematics. His most influential work relates to three areas: the general properties of functions, as presented in his ‘calculus of lambda conversion’; the theory of computability and the decision problem, to which he made fundamental contributions, known as Church’s thesis and Church’s theorem; and intensional logic, developing Frege’s theory of sense and denotation. In the last four decades of his life Church continued working mostly in this last area.